The invention relates to a method for manufacturing a data carrier, an inlay for a data carrier, as well as to a data carrier itself. The invention relates in particular to a method for manufacturing a contactlessly readable data carrier with integrated IC, which can be used as a chip card, identification document, identity card or as a data page in a passport booklet.
A portable data carrier is basically a computer with a reduced overall size and resource range, which has a microcontroller and at least one interface for communication with an external device. It frequently possesses no, or only a rudimentary, dedicated user data output. Its outer construction form is so designed that it can be easily carried by a user at any time. Preferably, a data carrier is equipped with corresponding security functionalities, for example in the form of a smart card, chip card, mass memory card, multimedia card. For example a payment card, such as credit or debit cards, is a data carrier as it is described herein. Alternatively, it is an electronic identity document, such as for example an electronic national identity card, a passport, having machine-readable identification data of a person stored on a chip.
Portable data carriers now increasingly have a contactless interface. The operating system of the chip card is here so designed that the contactless interface can exchange data for example according to one of the protocols described in the standards ISO/IEC 14443, 15693 or 18092. Additionally, a contact-type interface, for example according to ISO/IEC 7816, can further be operated parallel. For this purpose, the data carriers are provided with transponder arrangements consisting of a chip and a near-field communication antenna connected therewith. For the sake of simplicity, in the following there will be employed the term coil instead of near-field communication antenna. These chip-coils arrangements allow to contactlessly read data stored in the IC and/or to contactlessly write data thereto. The manufacturing of such data carriers is typically effected by laminating at least one core layer and two cover layers, the chip-coil arrangement being integrated into the core layer. Such constructions are also referred to as inlays.
A problem with respect to the durability of such data carriers is the bond between the chip and the data carrier body. The two consist of different materials, the chip is hard and high-melting, while the material employed for the data carrier body is comparatively soft and readily laminatable. The different material constitutions of chip and data carrier body lead upon long-term use sometimes to the formation of cracks emanating from the border region between chip and data carrier body and continuing in the bordering layers.
A cause for the formation of cracks can be found in the mechanical load on the data carriers, by means of which the mechanical tensions frozen in the data carrier body are released. The mechanical tensions could have been introduced into the data carrier body, for example, during the lamination. In particular, a formation of cracks or, likewise, a breaking of a layer of the data carrier body, for example of a foil layer occurs. These cracks may propagate into the nearest foil layer. In particular the electrical functionality, the appearance, the ruggedness against external environmental influences and also the mechanical stability of the data carrier are impaired by the cracks. In extreme cases, the electrical functionality of the data carrier, in particular the contactless reading of/bringing data from/into the IC of the data carrier is no longer possible.
From the G&D print DE 4040770 A1 it is known to cover a carrier band having chips with a thermoplastic layer. Upon placing the chips into the card body the adhesive is activated by means of pressure/heat and ensures a stress-free bond of chip and card body.
From the WO 2009/135823 A1 there can be inferred a construction for a multilayer body of a data carrier body in which individual layers contain inserts made of a softer plastic material. A chip to be integrated into the data carrier body is arranged exactly in such a patch made of softer plastic material. The extension of the patch here is larger than the chip. During the lamination this plastic material softens and is arranged around the module thereby. In this way, stress zones leading to cracks can be prevented. The realization of the patchwork-like layers is elaborate, however, and, moreover, the plastic material is difficult to position.
In the DE 10 2010 025 774 A1, before the chip module is inserted into the card layer construction, a chip is wetted with an adhesive agent and placed into the card body. Thus, components adverse to lamination are made connectable during the lamination, without the occurrence of microcracks being possible. The chip module is treated before it is placed into the card body, so that a good adhesive connection between chip module and data carrier body can be obtained.
In the DE 10 2009 050 753 A1 there is described a manufacturing method for data carriers, in which a chip module is arranged on a carrier substrate. A liquid UV adhesive is employed for configuring an intermediate layer by means of appropriate shaping. Then, a cover layer is laid on. Then, the UV adhesive is cured by means of UV radiation, the data carrier singled and then laminated.
In the book, “Vom Plastik zur Chipkarte” by Y. Haghiri, T. Tarantino, Carl Hanser Verlag, Munich, 1999, there are described manufacturing methods for chip cards, in particular the lamination technique.
The problem in all of these propositions is that the mechanical tensions between chip, electronic components and data carrier body, which were introduced during the lamination, cannot be sufficiently compensated, because adhesive and chip form a mechanical unit already before the lamination. This leads to mechanical tensions in the data carrier during the lamination. Upon proper use of the data carrier, these tensions lead to the described formation of cracks.